I used a Hotmail account to registered for Window Live. Now I do not want that specific Hotmail account. Can I use a new a/c to register? Will I lose all previous data?
If you register a new account, you are unable to transfer any of your purchases (apps, games, etc). However if you only want to change the account name you can set up aliases linked to the original account using the control panel at https://account.live.com/names/Manage.
Note that if you want to sign into your Windows Phone with one of these new aliases you will have to factory reset the device. However you can have up to 10 Live accounts on your phone, so if you only wanted to start sending and receiving to and from the new address you can simply add the additional account and switch off email syncing on the old one.